OP, to your point of value of M3 sedan vs. coupe, there were fewer sedans manufactured vs. coupes. I don't have the percentages but if I recall correctly, it is by a significant amount. The seems to be a demand for the sedans but same can be said of the coupes. IMO, go with the model that best meets your needs and/or desire. In general, the M3 will hold it's value. Both might take a depreciation hit depending on how the audience takes to the upcoming M3/M4.